
// Data types
// The latest ECMAScript standard defines seven data types:
// Six data types that are primitives:
    // Boolean
    // Null
    // Undefined
    // Number
    // String
    // Symbol (new in ECMAScript 6)
// and Object


// Null type
    // The Null type has exactly one value: null. See null and Null for more details.
// Undefined type
    // A variable that has not been assigned a value has the value undefined. See undefined and Undefined for more details.
// http://www.ruanyifeng.com/blog/2014/03/undefined-vs-null.html
// http://stackoverflow.com/questions/801032/why-is-null-an-object-and-whats-the-difference-between-null-and-undefined
// http://stackoverflow.com/questions/5076944/what-is-the-difference-between-null-and-undefined-in-javascript

var foo
console.log(typeof foo)
var foo = null  // foo is now a object
console.log(typeof foo)
// [为什么JavaScript里面typeof(null)的值是"object" ](https://www.zhihu.com/question/21691758)
var foo = 42;    // foo is now a Number
console.log(typeof foo)
var foo = 'bar'; // foo is now a String
console.log(typeof foo)
var foo = true;  // foo is now a Boolean
console.log(typeof foo)
var foo
console.log(typeof foo)


function test(){}
console.log(typeof test) // 'function'
console.log(test instanceof Function) //true
console.log(test instanceof Object) //true
// http://stackoverflow.com/questions/35185871/what-is-functions-data-type-function-or-object-in-javascript

// <<<<<<< HEAD

var undefine;
var num = undefine;
// =======
console.log("...........................")
var testValue = 1;
testValue = 1+"";
console.log(typeof testValue)
// >>>>>>> 8987307907162de68be627ab8a4cb1b8a94c07c7
